George Clooney has been called as a witness in Silvio's Berlusconi's trial in Milan for paying an underage prostitute for sex.

Berlusconi is accused of paying cash and jewels to Karima el-Mahroug, the dancer known as Ruby the Heartstealer when she attended his so-called "Bunga Bunga" parties in 2010, aged 17.

Mahroug has denied she slept with Berlusconi, but has told prosecutors of risqué scenes at Berlusconi's mansion outside Milan. She also claimed she saw Clooney at one of the parties.

The actor has previously denied being present and has been called to appear next Friday as a witness by the former prime minister's lawyers in an attempt to discredit Mahroug.

Clooney said last year he had spoken with Berlusconi's legal team and was happy to testify to put the record straight. His former girlfriend, Italian showgirl Elisabetta Canalis, has also been called.

The actor has revealed he did spend one night at Berlusconi's home in Rome, which he described as "one of the more astonishing evenings of my life". Arriving to discuss Darfur with the then prime minister, Clooney said he was taken to Berlusconi's bedroom to see the bed that Vladimir Putin gave him, and was then asked to stay for a party.

Berlusconi made a surprise speech in court on Friday, denying having "intimate relations" with Mahroug and ruling out any "scenes of a sexual nature", at his parties in Milan, saying they were merely costumed shows "about which there was nothing vulgar".

Women attending the parties have described guests dressed as nuns and footballers performing stripteases.

Berlusconi also denied putting pressure on police to release Mahroug from custody in May 2010 after she was arrested on suspicion of theft.

Berlusconi appeared in court after supporters tried in vain to insert amendments into a new anti-corruption law edging through the Italian parliament which would have cancelled out the charge against Berlusconi of abusing his authority with the police.